Continuous mining machine and method



1966 H. E. CARVER 3,288,532

CONTINUOUS MINING MACHINE AND METHOD Filed March 10, 1964 3 Sheets-Sheet l AVAVAVAVAVAVAVAVA Ch a: 52 d5 .54 58 /2 g EL; 60

INVENTOR.

fl4/30L0 t. CAAI ER Nov. 29, 1966 H. E. CARVER CONTINUOUS MINING MACHINE AND METHOD 5 Sheets-Sheet 2 Filed March 10, 1964 FIG-- 10 INVENTOR.

AU'TOR/VEY Nov. 29, 1966 H. E. CARVER 3,288,532

CONTINUOUS MINING MACHINE AND METHOD Filed March 10. 1964 :5 Sheets-Sheet 5 F 017/144 f/d/V H4ROLD CARI ER United States Patent 3,288,532 CONTINUOUS MINING MACHINE AND METHOQ Harold E. Carver, Brea, Calif., assignor to Union 01] Company of California, Los Angeles, Calif., a corporation of California Filed Mar. 10, 1964, Ser. No. 350,877 29 Claims. (Cl. 299-18) This invention relates to a method and apparatus for continuous subterranean mining and tunneling, and more particularly to an improved method and apparatus for the continuous mining of oil shale and other mineral deposits.

The method and apparatus of my invention employs a new principle of tunnel mining resulting in the subterranean deposit being removed in substantially large pieces with only a minimum amount of deposit being reduced to small size particles. By use of my novel method and apparatus, a relatively large diameter tunnel is bored through the formation to yield the mined product. Successive adjacent tunnels can be bored in large deposits, such as are typical of oil shale deposits, or the tunnel can follow a particular seam or vein where the extent of the deposit is more limited. In either case, boring is accomplished by a power-driven mining apparatus which tunnels through the formation by a stepwise grooving and shearing process. A plurality of varying diameter grooves, or kerfs, are cut into the formation in a generally conical configuration about the axis of the bore. The projecting cores formed by the grooves are then sheared from their attachment to the formation in such manner that relatively large pieces are formed. These pieces are removed from the cuttingarea and the machine moved forward in the bore to the next cutting position. The bore through the formation is formed by successive repetition of this stepwise cutting method wherein the bore is enlarged by removal of successive cores until the ultimate tunnel diameter is realized. Although my invention relates primarily to a machine and method for mining oil shale, it is equally useful in any mining or tunneling application, particularly where the production of fine particles is undesirable.

Most conventional shale oil retorting processes require a shale feed consisting of particles larger than /s-inch size, as fine particles agglomerate and tend to plug the retort. The fines portion of the oil shale is usually removed by screening prior to retorting and must be either discarded or subjected to specialized retorting. In either case, processing costs are increased since discarding the fines results in a loss of both potential oil recovery and increased mining expense, and alternately, the specialized processing necessary for fines retorting results in addi-' tional cost. Employment of a mining method which results in production of a low proportion of fines is therefore essential to the overall economics of most shale oil programs.

Subterranean deposits of oil shale can be recovered by any one of several different mining methods known in the prior art. The conventional room and pillar method, wherein the excavation is accomplished by drilling and blasting, is one such method. Room and pillar mining, accompanied by conventional crushing, is particularly attractive from the standpoint of product particle size as approximately 95 percent of shale produced by this method is in the form of particles larger than As-inch in size. Accordingly, the fines portion less than Aa-inch in size, requiring discarding or special treatment, is only about 5 percent. Although the room and pillar method is attractive because of relatively low fines production, the overall cost per ton of shale removed is an estimated 18 to 20 percent higher than the cost of some of the continuous boring methods previously available for mining and tunneling. The low operating cost of these continuous boring machines, however, is offset by excessive fines production, the proportion of particles less than inch in size being as high as 50 percent of the mined product. Considering these factors, it is essential that the most economical method of mining be employed, as the cost of mining is one of the major items in the overall cost of shale oil recovery. There is, therefore, considerable economic incentive to utilize a continuous mining method if satisfactory mined product can be attained. Both of these criteria are achieved by the method and apparatus of my invention wherein the yield of fine partieles less than As-inch in size is approximately 8 percent, or less, andthe operating costs are comparable to or lower than those of other continuous mining methods.

Prior art continuous boring and tunneling machines all commonly produce the tunnel by. operating directly on the fiat face of the formation lying perpendicular to the principal axis of the tunnel. Although a number of different cutting methods are utilized, most prior art methods require removal of material from the face of the out directly by some form of attrition, or by the technique of cutting a series of axial grooves into the flat face to form cores which are thenremoved by crushing, or other means. Some of the smaller machines utilize the screw auger principle, but these machines lack sufiicient capacity for large scale mining operations. Particle size control has long been a problem in mining operations, and axial fiat-face grooving and core breaking methods were developed in an attempt to reduce the quantity of fines produced by other boring methods primarily relying on attrition for cutting. However, even though the axial groove can be successfully cut into the face of the formation, no satisfactory method of core removal has been previously developed whereby these cores are removed in relatively large pieces. Accordingly, the advantages sought to be achieved by prior art groove cutting techniques have been minimized.

Numerous different core breakers have been developed, such as crushers, shear breakers, and screws, respectively disclosed in US. Patents 3,008,698 to Risse et al., 3,010,- 708 to Hlinsky et al., and 2,754,099 to Tracy. Each of these devices, however, fails to achieve a low fines yield as they are incapable of exerting a maximum force at the root of the core parallel with the plane of attachment, but must instead operate on the outer face of the core, or in the groove close to the surface of the face. Thus, whether the compressive crushing force is applied perpendicular to the plane of attachment by means of core crushing disks and rollers, or whether stress force is applied by means of wheels or wedge devices operating in the grooves, the result is to shatter the formation into small fragments rather than causing the core to be severed from its attachment to the formation in relatively large pieces. A particularly advantageous feature of my invention is the novel technique of groove cutting which permits the application of an external force at the core root parallel with the plane of attachment, thus causing core segments to be sheared off in relatively large pieces.

Another disadvantage of prior art boring devices is the relatively high power consumption required to achieve the unnecessary and undesired size reduction. The power requirement is particularly high in the case of compression breakers as the compressive strength of oil shale has been found to be about five times as high as its shear strength. Therefore, not only is the power consumption high because of the unnecessary size reduction, but additional power is required because of the high resistance to crushing.

It is therefore among the objects of my invention to 3 develop an improved continuous boring device suitable forthe mining of oil shale and other mineral deposits and for the boring of tunnels and conduits for various purposes.

Another object of my invention is to provide an improved method of mining whereby the mined product is recovered in relatively large pieces and the production of particles of fine size is minimized.

A further object of this invention is to provide a mining machine and method utilizing the principles of groove cutting and shear core breaking, whereby the cores are primarily removed by the application of shear force applied at the core root.

A still further object of this invention is to provide a novel continuous boring method and apparatus whereby boring is accomplished with decreased power consumption.

Other objects and advantages of this invention will become apparent to those skilled in the art by study of the description and illustration thereof contained herein. I have found that the foregoing objects and their attendant advantages can be realized by continuous mining of oil shale, or like mineral deposits, utilizing a machine which produces a tunnel through a subterranean formation by successive repetition of a stepwise process wherein a plurality of varying diameter, concentric grooves are cut into the formation around the periphery of the bore, the grooves being disposed along the principal axis of the tunnel in a generally conical con figuration. The grooves may be cut radially into the formation in a direction perpendicular to the principal axis of the tunnel, or they may be cut into the exposed faces of the formation parallel to the principal axis. The protruding annular rings or cores formed by the grooves are then removed by the application of force to the exposed face of the core at the core root adjacent to the point of attachment to the formation, which causes them to break away from the formation in relatively large pieces. Whether the grooves are cut radially or axially, the core breaking force is applied at right angles to the direction of grooving. The broken core pieces and cuttings are removed from the cutting area and the machine advanced forward into the bore to a new cutting position.

My invention will be more readily understood by reference to the accompanying description and drawings of which:

FIGURE 1 is an elevation view schematically depicting the mining machine of my invention in operation in a mine tunnel;

FIGURE 2 is an elevation view of the cutting head;

FIGURE 3 is an end view of the cutting head depicting the relation of the hydraulically operated groove cutters and core breaking disks; I

. FIGURE 4 is a detail showing a typical groove cutter assembly;

FIGURE 5 is a sectional view of the formation schematically depicting a radial groove cutting operation;

FIGURE 6 is a section view of the formation schematically depicting the axial breaking of cores formed by radially cut grooves;

FIGURE 7 is a sectional view of the formation schematically depicting an axial groove cutting operation;

FIGURE 8 is a section view of the formation schematically depicting the radial breaking of cores formed by axial grooves;

FIGURE 9 is a schematic illustration showing alternate methods of positioning the groove cutting tools;

FIGURE 10 is a schematic illustration showing an embodiment of my invention utilizing counter-rotating cutter heads; and

l FIGURE 11 is a schematic illustration of a method of mounting the groove cutters and core'breaking disks on the cutting head.

Referring now to one embodiment of my apparatus, there is illustrated in FIGURE 1 a mining machine 10, shown in the operation of boring into a formation, having a power-driven rotary cutting head 12 mounted at the front end of an elongated main frame 14, this structure being supported on crawler tracks 16. Rotary cutting head 12 is attached to and supported by shaft 18 and is driven through shaft 18 and speed reducer 22 by power unit 20, also fixedly attached to frame 14. Power unit can be an electric motor as shown, or a gas, gasoline, or diesel powered internal combustion engine and can consist of a single unit, as illustrated, with power takeolfs to drive cutting head 12, crawler track 16, conveyor 32 and a hydraulic pump, not shown, or alternately, separate power units can be provided for each drive requirement. Alternately, cutting head 12 may also be rotated by means of hydraulic power. In the 7 preferred embodiment, electric motors are used for all tion of the machine frame in the bore.

power means. Power unit 20 is smaller than might be expected from experience with previous continuous mining machines because of the lower overall power require ment of my process and because sequential stepwise grooving, core breaking and forward movement does not develop peak power demands as in other machines. The

speed of rotation of cutting head 12 is usually reduced from the normal motor rotating speed of power unit 20, by speed reducer 22, to a speed within the range of from about 0 to about 10 revolutions per minute, a preferred operating speed within this range being from about 1 to about 6 revolutions per minute. Speed reducer 22 contains a clutching mechanism, not shown, to.

connect and disconnect cutting head 12 from power unit 20. Speed reducer 22 can comprise a variable speed unit, not shown, so that the fixed speed of power unit 20 can be converted to variable cutting head rotative speeds. ,Alternately, cutting head speeds can be con Because of the frictional resistance of the earth to the rotary motions of cutting head 12, torque is developed which tends to cause the entire machine to rotate around the axis of shaft 18. Anti rotation jacks 26, also known as torque reactors, are provided to prevent rota are located on each side of mining machine 10, of which only the right jack 26 is illustrated in FIGURE 1. Jack shoes 26 are hydraulically extended to each side of the Opposing jacks.

bore tunnel by the expansion of a hydraulic piston, not

shown, in hydraulic jack cylinder 34. Jack shoes 28 engage the tunnel wall to prevent rotation of the machine in the tunnel. Anti-rotation jacks 26 can be constructed so that they are slidably m'oveable in a horizontal direction along the principal axis of the bore, yet are rigidly fixed in the vertical direction to prevent rota-1 tion of the machine. In this manner, jack shoes 28'cant be brought into contact with the tunnel walls, thus preventing rotation 'of the machine, yet mining machine. 10 is free to move in an axial direction over a limited! distance without repositioning of anti-rotational jacks 26'. on the tunnel wall. Cutting head 1 2 -can be constructed" in two sections and geared in such mannerthat-one'sem. tion is driven clockwise around shaft 18' whil'ethe other:

section is rotated counter-clockwise at thesame. or a difierent rotative speed. The torque developed by the frictional resistance of the formation to the 'rotary cut-- ting action thus will becounter-balanced and the need for jacks 26 will be minimized or eliminated. FIGURE schematically depicts two such counter-rotating cutting heads 12a and 12b mounted on shaft 18. This same result can be achieved by mounting two counter-rotating cutting heads side by side.

On severance from the formation, the mined product falls into collection bin by means of gravity and the rotative motion of the core collectors, to be more fully described hereinafter. Collection bin 30' is positioned at the extreme forward end of frame 14, adjacent to the lowest extremity of cutting head 12, in such a way that the min-ed product can flow from revolving cutting head 12 into bin 30. The mined product is moved from collection bin 30 to the rear of mining machine 10 by conveyor 32, whereupon it can be removed from the bore tunnel by conventional means such as conveyors, trucks, mining cars and the like.

One embodiment of the cutting head of this invention is shown in FIGURES 2 and 3. Cutting head 12 comprises frame 52 fixedly attached at its forward and rear extremities to shaft 18 so that cutting head 12 rotates about the central axis of shaft 18 as the shaft is rotated. Hydraulically positioned groove cutters 54 are attached to frame 52 so that the cutting tools can be radially extended and retracted in a direction substantially perpendicular to the principal axis of the bore. Although only four groove cutters are specifically identified at 54, all the groove cutters are of similar construction and function. As shown in FIGURES 2 and 3, companion groove cutters 54 are opposite one another, 180 degrees apart on frame 52, so that companion cutters will operate in the same groove. Alternately, groove cutters 54 may be staggered in such a manner that no groovecutter is opposite another on frame 52 in which case each groove is cut by an individual groove cutter.

Core breakers 58 are positioned on the outer edge of frame 52 in such relation to groove cutters 54 that the cores formed by the radial grooves in the formation will be sheared from their attachment to the formation by pressure exerted by core breakers 58 rolling against the exposed face of the core. Although only four core breakers are specifically identified at 58, all core breakers are similar in construction and function. Core breakers 58, basically flat circular disks with pointed or sharpened edges, freely rotate around individual support axles (not shown) which in turn are attached to frame 52 at the periphery thereof. Alternately, core breakers 58 may comprise disks shaped as truncated cones. In such case, the cone base is positioned adjacent the formation, the beveled edge bearing against the core. Core breakers 58 are each caused to rotate about their individual axes by rolling on the exposed formation face as cutting head 12 rotates about the central axis of shaft 18. Alternatively, core breaking disks 58 can be mounted on hydraulically extendable arms so that the disks can be brought to bear against the exposed vertical face of the cores by extension of the arms. In such case, mining machine 10 would remain locked in a fixed position in the mine tunnel during the core breaking operation and the external force required to cause the cores to be sheared from the formation would be developed by the hydraulic extension of core breakers 58. In either case, core breakers 58 exert a force parallel to both the principal axis of the tunnel and to the plane of attachment of the core to the formation. One method of mounting groove cutters 54 and core breakers 58 on cutting head frame 52 is illustrated in FIGURE 11, wherein a non-extendable core breaker installation is seen.

The initial bore or pilot hole is made by auger-type pilot bit 60 located on the extreme forward end of shaft 18. As cutting head 12 rotates, auger bit 60 turns into the formation to cause the initial penetration thereof. The pilot hole is enlarged by cutters 62 located at the periphery of the foremost extremity of frame 52. Any convenient means of making the initial penetration can be used in lieu of anger bit 60 and pilot hole cutters 62. Referring now particularly to FIGURE 3, there is illustrated an end view ofcutting head 12 further showing the location and orientation of groove cutters 54, core breakers 58 and cutters 62. In this embodiment, frame 52 comprises two structure elements arranged 180 degrees opposite each other around shaft 18. However, instead of this arrangement, frame 52 can be comprised of three, four, or more of such elements arranged at angles of degrees, 90 degrees, or less, respectively, around shaft 18; Also, a modified groove cutter installation can be utilized wherein two or more groove cutters 54 are located adjacent to each other on frame 52 so that several groove cutters function to cut the same groove. The number of groove cutters 54 functioning to cut a single groove may be varied in a particular machine, depending on the diameter of the groove being cut. Core collectors 64 comprise curvilinear baffles extending from the front portion of cutting head 12 to the rear thereof and flaring away from frame 52 at the rear. As cutting head 12 rotates, core collectors 64 function as rakes to assist gravity forces in moving the mined product toward the rear of cutting head 12, whereupon it is deposited in collection bin 30.

Groove cutters 54, illustrated more fully in FIGURE 4, comprise hydraulic cylinder 70 containing a hydraulic piston, not shown, to which cutting tool holder 72 is attached. Replaceable insert bit 76 is removably attached to cutting tool 74 which in turn is removably inserted into cutting tool holder 72 to permit exchange of cutting tools for sharpening, rotation, or replacement of insert bits 76. Cutting tools 74 can be constructed so that each tool holds a plurality of insert bits 76, each set to cut in the some groove at a slightly lower depth than the preceding bit. Cutting tool 74 is extended and retracted by supplying hydraulic fluid under pressure to one or the other side of cylinder 70 to cause the piston to move within the cylinder. Although insert bits76 may be constructed with any geometric form, a preferred bit has been found to consist of a small fiat disk removably attached to cutting tool 74 in such manner that it does not rotate about its point ofattachm'ent. The circular bit has a relatively long cutting surface, since it is in contact with the formation along approximately one-ha1f of its circumference, which tends to increase bit life. Bit life may also be extended by rotating insert bits 76 approximately degrees to achieve a second run, then reversing the bit for two more runs. Thus, bit life can be increased four fold by this technique. Alternately, insert bits 76 can be rotatably attached to cutting tool 74 so that they freely rotate about their point of attachment during the cutting operation. Although insert bits 76 can be fabricated from any material possessing the necessary strength and wear characteristics, tungsten carbide has been found to be one preferred material. Groove cutters 54"can' be mounted in such manner that hits 76 contact the formation surface at an angle, either positively or negatively inclined from the radius of cutting head 12, as illustrated in FIGURE 9. Alternately, cutting tool 74 can be bent insuch manner that insert bits 76 contact the surface at the proper angle, hydraulic cylinders 70 then being mounted radially. Superior results are achieved when insert bits 76 contact the surface to be cut at a negative angle; that is an angle such that they trail hydraulic cylinder 70 as cutting head 12 rotates. In the practice of my invention, the most forward, or pilot penetration, into the formation is made by augertype pilot bit 60 and by cutters 62 located at the extreme forward end of mining machine 10. Thereafter, the boring operation consists of enlarging this small bore to the ultimate tunnel size by the grooving and core breaking process described herein. Normally the tunnel formed according to this method is substantially circular in cross-section, although various shaped tunnels may be formed by using a plurality of cutting heads mounted side by side. The entire boring operation takes place in the cutting area adjacent to the most forward penetra tion of the tunnel into the formation. Once the tunnel is enlarged to the ultimate desired diameter, no further cutting is necessary or occurs along the length of the completed tunnel. The cutting area, where enlargement of the pilot bore occurs, comprises a series of concentric tunnel sections of varying diameters increasing from that of the pilot bore to the ultimate tunnel diameter. Whether the radial or axial grooving technique is employed, each of these tunnel sections consists of a peripheral exposed wall face substantially parallel to the principal axis of the tunnel and a substantially perpendicular face or step where the tunnel diameter is enlarged to that of the next adjacent section. I

One embodiment of the stepwise mining method of my invention, comprising radial groove cutting and axial core breaking is illustrated in FIGURES and 6. Enlargement of the pilot bore to the ultimate tunnel diameter is achieved by removal of annular cores formed by cutting a plurality of radial grooves into the formation around the periphery of the bore, or cutting area. Referring particularly to the grooving operation illustrated in FIGURE 5, two typical cutting tool 74 and insert bit 76 assemblies are seen in the process of cutting radial grooves 102 into exposed parallel peripheral faces 100. Cutting tools 74 are hydraulically extended radially from shaft 18 until insert bits 76 contact the surface of the formation. Cutting is achieved by bits 76 rubbing against the formation as cutting head 12 is rotated. Cutting tool 74 is further extended as grooves 102 are deepened to their ultimate depth. Grooves 102, shown in cross-section in FIGURE 5, are cut into parallel face 100 adjacent to face 106, the perpendicular face of the next smaller tunnel section. Grooves 102 are substantially uniformly disposed along and concentric to the principal axis of the tunnel, and substantially uniformly increased in diameter from the forwardmost groove rearward. Cutting of grooves 102 into the subterranean formation forms annular protrusions or cores 104 bounded by groove 102, by exposed parallel face 100, and by previously cut perpendicular face 106. Core 104 remains attached to the formation at the root, or unexposed fourth side. Core size is determined by spacing between adjacent grooves 102 and the depth thereof. The spacing of grooves 102 can vary from less than 3- inches to about l2-inches or more, a preferred groove spacing being about 6-inches. Too close spacing results in a high proportion of fines from the groove cutting, since approximately 85 percent of cuttings are less than %-inch in size. Wide spacing, on the other hand, results in core segments which are difiicult to handle because of their size and weight and which might require additional crushing prior to retorting. The depth of groove 102 in the formation wall will determine the point at which the core may be sheared off. Although grooves 102 can be cut to any depth, it is convenient to cut them to a depth equal to the groove spacing. No matter what groove spacing and depth are selected, all grooves are preferably substantially uniformly spaced and cut toa substantially uniform depth so that on removal of cores 104, the forward movement of cutting head 12 will not be impeded. Grooves 102 can be of any convenient width, the preferred groove being as narrow as practical to avoid unnecessary production of fines and to reduce bit Wear. I have found that grooves five-eighths inch wide can be conveniently cut with drag bit cutters of the type described herein.

The cutting of the grooves described herein can be accomplished at reasonably attainable bit pull and bit thrust forces whether the grooves are cut radially or axially. Bit pull is the force required to move a cutting tool through a formation in the direction of cutting. Bit thrust is the force necessary to engage the cutting tool with the surface to be out. In my machine, bit thrust is the force required to extend cutting tools 74 during the cutting operation, and bit pull isthe resistanceto rotation of cutting head 12. Bit thrust is mostly supplied by the hydraulic system, whereas the bit pull force is supplied by power unit 20 through speed reducer 22 and shaft 18. The principal variables-affecting groove cutting forces are the formation type, bit penetration, lineal bit velocity, and cut angle; cut angle being defined as the penetration in inchesper foot of lineal bit travel. Cutting forces increase as the cutting angle is increased. 'Low cut angles, on the other hand, require increased groove cutting time. Cut angle, therefore, becomes an economic balance between the cost required to provide the increased force and the value of the additional capacity achieved thereby. These factors require special consideration with the varying cutting head diameters of my invention, particularly since bit velocities are considerably higher at the larger diameters of cutting head 12. Typically, I have found that grooves can satisfactorily be cut into oil shale formations of 16 to 41 gallons per ton oil assayat bit penetrations of 0.01 to 0.10 inch per revolution of cutting head 12 and lineal velocities of -120 feet per minute. Bit life can be extended by cooling bits 76 with water or other convenient cooling means.

Although the embodiment of my invention described herein utilizes drag bit cutting to form radial grooves 102, other methods of cutting can be effectively utilized. Substitution of rotary saw blades for cutting tools 74, though somewhat more complex, has the advantage of cutting a narrower groove, thus further reducing the proportion of fines produced.

' On completion of the groove cutting step, cutting tools 74 are hydraulically retracted and cores 104 formed by the plurality of varying diameter concentric grooves 102 are removed as illustrated in FIGURE 6. Cutting head 12 is moved forward in the bore so that core breakers 58 bear against the roots of cores 104 substantially opposite the bottom of adjacent grooves 102 in suchmanner that the external force is applied substantially parallel with the plane of attachment of core 104 to the formation. As cutting head 12 rotates, causing core breakers 58 to scribe concentric circles on the exposed substantially perpendicular face 106 at the core root, shear forces are created which cause core 104 to be broken from the formation by cracking at the root. These stress planes and incipient cracks are depicted at 108. As cores 104 are severed from the formation, they break into segments which are usually of a size convenient to handle, typical segments being less than four times the groove spacing in length. Several revolutions of cutting head 12 are usually sutficient to generate the necessary internal stress to cause cores 104 to be severed from the formation. Although core breakers 58 penetrate into the formation to some extent, core removal is primarily caused by the stresses created in the formation rather than by a cutting action. Cutting head 12 rotates throughout the core breaking operation tending to cause severed sections of the cores to be cleared away and conveyed, by means of core collectors 64 and conveyors 32, to the rear of mining machine 10. Although cores removed in this manner generally break cleanly at the core roots, it may be necessary for cutting head 12 to perform a minor amount of reaming as the machine moves forward in the bore to a new grooving position. Cutting'bits, not shown, may be installed at the periphery of frame 52 to facilitate this reaming action. On, completion of this forward move, mining machine 10 is in position to repeat the process described above by cutting another series of grooves 102 to form a subsequent series of annular core sections 104. Thus, by successive removal of these annular cores, the bore is widened from the original pilot hole diameter to the ultimate tunnel size.

Considerable external force is required to generate sufficient internal stresses in the cores to cause them to be sheared from the formation as core breakers 58 are brought to bear against the face of the formation. This force can be generated by any one of several conventional methods of propelling mining machine forward in the bore during the core breaking operation. Forexample, the necessary force can be derived by means of crawler tracks such as disclosed in US. Patent No. 2,841,378 to Ovsky. US. Patent No. 2,998,964 to Morlan discloses the use of a hydraulic jacking system to propel a mining machine forward against a formation face, which jacking system can be adapted to propel the machine of this invention forward in the bore to generate the force necessary for core breaking. Kirkpatrick, in U.S. Reissue No. 24,965, teaches the use of a pilot pull device to move a mining machine forward in the bore hole. Kirkpatricks device can be utilized with my machine to generate the required forward thrust. Although it is critical that sufficient force to cause the cores to be sheared from their attachment to the formation and to move the machine forward in the bore be genera'ble, the particular method of propelling mining machine 10 forward is not critical, and any convenient means of propulsion can be utilized. As disclosed above, the required core breaking force can alternately be generated by holding mining machine 10 stationary in the bore and hydraulically extending core breakers 58 against the core roots.

Although a preferred embodiment of my invention 'according to the foregoing description utilizes radial groove cutting and axial core breaking, satisfactory results can also be obtained by an alternate method of axial grooving and radial core breaking illustrated in FIGURES 7 and 8. In this modification, mining machine 10 is constructed essentially as described above, except that the orientation of groove cutters 54 and core breakers 58 are reversed from those adapted to radial groove cutting. Groove cutters 54 are positioned on frame 52 so that they can be axially extended in the direction of penetration of the bore. By this means, a series of concentric grooves of increasing diameters are cut into the perpendicular faces of the bore, substantially parallel to the principal axis of the tunnel and disposed along the axis thereof in a generally conical configuration. Referring particularly to FIGURE 7, two typical assemblies of cutting tools 74 and insert bits 76 are depicted in the process of cutting axial grooves 122 into exposed perpendicular faces 120. Cutting tools 74 can be mounted as disclosed previously and as illustrated in FIGURE 9. Protruding annular coresof subterranean formation 124 are formed by groove 122, perpendicular face 120 and previously cut surface 126. Cores 124 remain attached to the subterranean formation at the root, or fourth side, opposite and parallel to perpendicular face 120. The axial grooving of my invention overcomes the disadvantages of prior art axial grooving because it permitsthe application of force directly at the core roots substantially parallel to the plane of their attachment to the formation.

Protruding cores 124 are then severed from their attachment to the formation and broken into pieces of a size convenient for handling by application of an external force as shown in FIGURE 8. The external force is derived by hydraulically extending core breakers 58 radially from the principal axis of the tunnel so that they bear against surface 126 at the root of core 124 at a point substantially opposite the deepest penetration of groove 122. As cutting head 12 is rotated, core breakers 58 are rolled around the periphery of the bore and radially extended to develop the necessary internal stress to cause core 124 to shear from its attachment. These stress planes and incipient cracks are depicted at 128. On removal of the broken core segments, core breakers 58 are retracted and mining machine 10 is advanced into position to commence the next groove cutting step.

One advantage of this alternate method is that the force required to bring the machine into contact with the face of the cut is reduced since cores 124 are broken by a force exerted radially from the principal axis of the tunnel,

rather than parallelto the axis. Axial grooves 122 can be cut to the same width and depth as radial grooves 102 described above. Thus, each section will be increased from between about 6 inches to about 24 inches in diameter over the adjacent smaller section, and the depth of the grooves will vary from about 3 inches to about 12 inches. Another advantage of the axial grooving method is-that jack shoes 28 have a smoother surface to seat against as they are expanded, thus providing a better grip.

Although core removal by shear forces created by core breaking disks is a preferred method of severing the cores formed by grooving, any method of core breaking can be utilized. Such other methods of core removal include the use of disks or plow-type drag wedges operating in the groove to force the core away from the formation, the cutting of a transverse groove at the core root to sever the core from the formation, etc. The critical feature in core removal is that the cores should be severed cleanly at the core root to prevent the unnecessary formation of fines particles and to facilitate movement of the mining machine forward in the bore.

The above description refers to the grooves and annular cores formed thereby as being disposed along the principal axis of the tunnel in a generally conical configuration. This configuration is not critical and cutting head 12 may be constructed so that the grooves and cores are disposed along the principal axis to form a hyperbolic, semi-elliptical, spheroidal or other convenient configuration. The size of the tunnel is determined by the diameter of cutting head 12 which can vary from relatively small machines of about S-feet or less diameters to large size machines with cutting head diameters of 40 feet or more. Although cutting head 12 can be of any size, limited only by design considerations, a cutting head with a diameter of about 30 feet is a preferred size for the mining of oil shale. The tunneling capacity of mining machine 10 is determined, in part, by the cutting head diameter. In setting the cutting head size, consideration should be given to the type of formation, the purpose of the bore and the rate at which it is desired to remove material from the formation.

Although there is herein shown and described one form in which my invention may be embodied, it will be understood that various changes and modifications in the invention may be attained without departing from the scope of the novel concepts of the invention, as defined by the claims hereof.

I claim: 1. A method of continuous mining in a subterranean formation comprising:

forming a substantially concave conical face having its vertex adjacent the point of deepest penetration into said formation, said face comprising a series of annular steps about its periphery which increase in diameter from said vertex rearward, each of said steps being formed by a radial face normal to the direction of penetration and an axial face parallel to the direction of penetration; cutting peripheral grooves into said formation adjacent the interior angles formed at the juncture of said axial faces with the adjacent next most forward radial face to form protruding annular cores of said formation, said grooves being concentric to and longitudinally disposed along the principal axis of penetration; and

severing said protruding cores from attachment to said formation by applying a shear force to the exposed faces opposite the deepest penetration of said grooves, said force being applied normal to said grooves.

2. The method of claim 1 wherein said grooves are cut radially from said principal axis of penetration, in planes perpendicular thereto.

3. The method of claim 1 wherein said grooves are cut parallel to said principal axis of penetration.

4. A method of continuous mining wherein a mining 1 1' machine is utilized to bore a tunnelthrough a subterranean formation by repetition of a series of steps comprising:

cutting a plurality of grooves around the periphery of a circular bore in said subterranean formation to form protruding annular cores of said formation, said grooves being concentric to and longitudinally disposed along the principal axis of said tunnel, said grooves uniformly inc'reasingin diameter from the forwardmost of said grooves rearward to form a generally conical configuration, said cores being defined by one of said grooves, an exposed face normal to said groove, and an opposite exposed face parallel with said groove, and remaining attached to said formation along one surface;

severing said cores from attachment to said formation by applying an external shear force to said oppositely exposed face of each of said cores substantially opposite the deepest penetration of said groove, said external force being applied in a direction substantially parallel to the plane of attachment of said core to said formation and substantially normal to the direction of groove cutting;

collecting and removing a major portion of said severed cores and material produced from said groove cutting operation from the cutting area; and

advancing said mining machine forward in said tunnel into position to commence a subsequent groove cutting operation.

5. The method of claim 4 wherein said grooves about said periphery of said tunnel are cut radially from said principal axis, in planes perpendicular thereto, said exposed faces of said cores lying substantially perpendicular to said principal axis, and said external force being applied against said exposed faces by advancing core breaking disks substantially parallel to said principal axis of said tunnel in the direction of penetration thereof, said core breaking disks bearing against said exposed faces at the place of attachment of said core to said formation and rolling against said faces to scribe a series of circles thereupon.

6. The method of claim 5 wherein said core breaking disks are advanced by extending said disks in the direction of said exposed perpendicular face with said mining machine held in a fixed position in said tunnel.

7. The method of claim 5 wherein said core breaking disks are advanced by moving said mining machine forward in said tunnel until said core breaking disks bear against said exposed perpendicular face, said core breaking disks being rotatably attached to said cutting head.

8. The method of claim 4 wherein said grooves about said periphery of said tunnel are substantially parallel to said principal axis thereof and in the direction of penetration of said tunnel, said exposed facesof said cores lying substantially parallel to said principal axis, and said external force being applied against said exposed faces by advancing core breaking disks radially from said principal axis of said tunnel, said core breaking disks bearing against said exposed faces substantially at the place of attachment of said cores to said formation and rolling against said faces to scribe a series of circles thereupon.

9. A method of mining oil shale and like mineral de posits by boring a tunnel through a subterranean formaforwardmost of said cores to the rearmost, said cores being formed by the cutting of a plurality of grooves in said subterranean formation about the periphery of said bore, said grooves being concentric to and disposed along said principal axis of said tunnel, in creasing in diameter from the forwardmost to the rearmost, said cores being severed from said formation by applying a shear force to an exposed face adjacent the base of said cores opposite the deepest penetration of said groove, said force being applied normal to said grooves, and said cores being broken into pieces as they are severed from said subterranean formation;

collecting and removing said broken core pieces and material from said pilot hole and groove cutting operations from the cutting area; and

advancing said mining machine forward in said tunnel to a new cutting position.

10. The method of claim 9 wherein said grooves about said periphery of said tunnel are between about /s-inch and about 3-inches in width and are cut radially from said principal axis, in planes substantially perpendicular to said principal axis thereof, said grooves being substantially uniformly spaced between about 3-inches and about 12 inches apart and cut to a depth substantially equal to said spacing.

11. The method of claim 9 wherein said grooves about said periphery of said tunnel are between about As-inch and about 3-inches in width and are cut substantially parallel to said principal axis of said tunnel, and in the direction of penetration thereof, to a depth of from about 3-inches to about 12-inches, each groove disposed along said axis being substantially uniformly increased in diameter between about 6-inches and about 24-inches over the next forward adjacent groove.

12. A method of recovering oil shale and like subterranean mineral deposits in pieces, a substantial portion of which, are larger than /s-inch size, by boring a tunnel through said deposits utilizing a mining machine employing a repetitive stepwise technique comprising:

rotating a power driven cutting head about the principal axis of said tunnel at a speed of from about 0 to about 10 revolutions per minute;

, maintaining said mining machine in a substantially stationary fixed position in said tunnel with relation to both axial and lateral movement therein;

gradually extending cutting tools mounted on said cutting head -radially from a retracted position to contact the peripheral surface of the bore wall so as to scribe radial grooves on the interior surface of said bore wall extending around the periphery thereof, said grooves being concentric to and longitudinally disposed along said principal axis thereof at substantially uniform distances of from about 3-inches to about 12-inches apart, the width of said grooves being substantially uniform and between about As-inch and about 3-inches, said grooves increasing in diameter from the forwardmost of said grooves to the rearmost thereof to form a generally conical configura tion about said axis;

continuing a radial cutting action by gradually extending said cutting tools while rotating said cutting head until the desired ultimate depth of grooves is reached, said depth being substantially uniform between about 3-inches and about 12-inches, and said grooves forming protruding annular cores of said subterranean formation, said cores remaining attached to said formation along one surface thereof; retracting said cutting tools;

advancing rotatable core breaking disks in the direction of penetration of said tunnel, generally parallel to said principal axis thereof, until said core breaking disks bear against the exposed perpendicular faces of said cores substantially at the place of attachment of said cores to said formation opposite the bottom of said grooves;

with said cutting head continuing to rotate about said principal axis of said tunnel, causing said rotatable core breaking disks to roll against said exposed faces so as to scribe a series of concentric circular paths thereupon until sufiicient internal stresses are developed in said cores to cause said cores to be severed from attachment to said formation and to break into pieces; collecting and removing a major portion of said broken core pieces and material produced from said cutting operations from the cutting area; and cutting a pilot hole in said formation while advancing said mining machine forward in said tunnel into position to commence the next groove cutting operation. 13. The method of claim 12 wherein one portion of said cutting head is rotated in a clockwise direction and a second portion of said cutting head is rotated in a counterclockwise direction about said principal axis of said tunnel.

14. The method of claim 12 wherein said core breaking disks are advanced by extending a plurality of arms upon which said core breakers are rotatably mounted.

15. The method of claim 12 wherein said core breaking disks are advanced by advancing said mining machine in said bore, said core breaking disks being rotatably attached to said cutting head.

' 16. A method of recovering oil shale and like subterranean mineral deposits in pieces, a substantial portion of which are larger than Az-inch size, by boring a tunnel through said deposits utilizing a mining machine employing a repetitive step-wise technique comprising:

rotating a power driven cutting head about the principal axis of said tunnel at a speed of from about to about 10 revolutions per minute; maintaining said mining machine in a substantially stationary fixed position in said tunnel with relation to both axial and lateral movement therein; gradually extending cutting tools mounted on said cutting head axially parallel to said principal axis and,

in the direction of penetration of said tunnel to contact the exposed facesof said subterranean formation lying substantially perpendicular to said principal axis of said tunnel, thereby scribing grooves on said faces about the periphery of said bore, said grooves being concentric to and longitudinally disposed along said principal axis of said tunnel so as to form a generally conical configuration, said grooves being of a substantially uniform width between about As-inch and about 3-inches, and each groove disposed along said axis being substantially uniformly increased in 1 diameter between about 6-inches and about 24-inches over the next forward adjacent groove;

continuing an axial cutting action by gradually extending said cutting tools, while rotating said cutting head, until the desired ultimate depth of groove is reached, said depth being substantially uniform between about 3-inches and about l2-inches, and said grooves forming protruding annular cores of said formation, said cores remaining attached to said formation along one surface thereof;

retracting said cutting tools;

extending core breaking disks attached to said cutting head radially from said principal axis of said tunnel until said core breaking disks bear against an exposed parallel face of said formation at a place substantially opposite the deepest penetration of said grooves;

with said cutting head continuing to rotate about said principal axis of said tunnel, causing said rotatable core breaking disks to roll against said exposed faces so as to scribe a series of circles around the periphery of said bore until sufiicient internal stresses are developed in said cores to cause said cores to be severed from attachment to said formation and broken into pieces;

collecting and removing a major portion of said broken core pieces and material produced from said cutting operations from the cutting area; and

cutting a pilot hole in said formation while advancing said mining machine forward in said tunnel into position to commence the next groove cutting operation.

17. The method of claim 16 wherein one portion of said cutting head is rotated in a clockwise direction and a second portion of said cutting head is rotated in a counterclockwise direction about said principal axis of said tunnel.

18. A mining machine for forming a tunnel in a subterranean formation comprising:

a mobile support structure;

a longitudinal shaft rotatably mounted on said structure;

a power means for rotating said shaft, said power means 7 being mounted on said mobile support structure;

a rotary cutting head rotatably mounted on said shaft and located at the forward end of said support struca plurality of groove cutting means mounted on said rotary cutting head for cutting grooves into said subterraneanformation about the periphery of a subterranean bore substantially concentric with and disposed longitudinally along the principal axis of said tunnel, each groove disposed along said axis increasing in diameter from the forwardmost of said grooves rearward, thereby forming protruding annular cores of said subterranean formation; and

i a plurality of core breaking means for severing said cores from attachment to'said subterranean formation, said core breaking means being mounted at the periphery of said rotary cutting head so as to act in a direction normal to said groove cutting means.

19. A mining machine for recovering oil shale and like mineral deposits from a subterranean formation comprisa support means for providing mobile support to said mining machine;

an elongated frame supported on said support means;

a power means mounted on said elongated frame for supplying the power requirements of said mining machine, said power means having a rotarydrive shaft located at the forward end of said support means;

a rotary cutting head mounted on said drive shaft, said rotary cutting head being generally tapered in shape, small at the forward end and larger at the rear end;

a plurality of groove cutting means mounted at the periphery of said cutting head for cutting grooves into said subterranean formation about the periphery of a bore to form protruding annular cores of said subterranean formation, said grooves increasing in diameter from the forwardrnost of said grooves rearward and being substantially concentric with and substantially uniformly disposed longitudinally along the principal axis of said tunnel;

a plurality of core breaking disks for severing said cores from attachment to said subterranean formation mounted at the periphery of said rotary cutting head, said disks being rotatably mounted on individual axles oriented so that said disks lie in a plane perpendicular to said groove cutting means; and

collecting and conveying means for collecting said severed cores and material from said groove cutting operation, and for conveying said collected material from the cutting area.

20. The apparatus of claim 19 wherein said rotary cutting head comprises two separately rotatable longitudinal sections, a first section of said rotary cutting head being rotated in a clockwise direction and a second section of said cutting head being rotated in a counter-clockwise direction around the axis of said cutting head.

21. The apparatus .of claim 19 wherein said groove cutting means comprise cutting tools extendable in a radial direction from the axis of said cutting head, and wherein said individual axles of said core breaking disks are 15 mounted on said cutting .head radially to said axis, said core breaking disks lying parallel to said axis of said cutting'head and extending beyond the periphery of said cutting head.

said cuting head parallel to said axis thereof, and wherein said core breaking disks are extendable in a radial direction from the axis of said cutting head, said core breaking disks lying perpendicular to said principal axis of said cutting head.

24. A mining machine comprising in combination: an elongated main frame having a forward end and a rear end; support means upon which said elongated main frame of said mining machine is supported, said support means providing mobility to said mining machine; power means for supplying the power requirements of said mining machine, said power means being attached to and supported on said main frame and having a rotatable drive shaft located at said forward end of said elongated main frame; a rotary cutting head located at the forward end of said main frame and fixedly attached to said rotatable drive shaft, said shaft providing support for said cutting head and imparting a rotative motion thereto, said rotary cutting head comprising a cutting head frame having a tapered shape, small at the forward end and larger at the rear end; extendable anti-rotation jack means mounted an each side of said main frame for maintaining said mining machine in a substantially fixed position in said tunnel;

propelling means for moving said mining machine in a subterranean mine tunnel;

a plurality of groove cutters mounted on the periphery of said cutting head frame comprising hydraulic cylinders fixedly attached to said frame having movable pistons contained therein for extending and retracting groove cutting tools attached to said movable pistons, said cutting tools having replaceable cutting bits attached thereto;

a plurality of core breakers mounted at the periphery of said cutting head frame, said core breakers comprising flat circular disks rotatably mounted on individual axles attached to said cutting head frame and orientated so that said core breaking disks lie in a 1 plane perpendicular to said-groove cutters, said-disks extending beyond said periphery of said cutting head frame;

collection and removal means attached to said main frame for collection of severed material from the cutting area and removing said collected material to the rear of said mining machine; and

pilot hole cutting means for making the initial penetration through said subterranean formation attached to said cutting head frame and rotating therewith, said pilot hole cutting means being located at the extreme forward end of said cutting head.

25. An apparatus according to claim 24 wherein said groove cutters are extendable in a radial direction from the axis of said cutting head and wherein said individual axles of said core breaking disks are mounted on said cutting head radially to said axis thereof, said core breaking disks lying in a plane parallel to said cutting head axis.

26. An apparatus according to claim 25 wherein said core breaking disks are mounted on extendable arms, said arms extending toward the forward end of said cutting head parallel to said axis of said cutting and said core breaking disks being mounted parallel therewith.

27. An apparatus according to claim 24 wherein said groove cutters are axially extendable toward the forward end of said cutting head parallel to said axis thereof, and wherein said core breaking disks are extendable radially from said axis, said core breaking disks lying perpendicular to said axis of said cutting head.

28. An apparatus according to claim 24 wherein said groove cutting tools are mounted so that said cutting bits contact the cutting surface at an angle.

29. An apparatus according to claim 28 wherein said cutting tool is inclined away from the direction of rotation so that said cutting bit trails said cutting tool as the cutting head is rotated.

References Cited by the Examiner UNITED STATES PATENTS 1,488,066 3/1924 Schmidt 29986- X 1,888,085 11/1932 Humbel 299 X 2,161,000 6/1939 Anderson 391 X 2,901,231 8/1959 Hagenbrook 299-87 X 3,092,190 6/1963 Gruere 299-87 X FOREIGN PATENTS 40,156 5/ 1929 Denmark. 253,799 11/1910 Germany. 135,179 3/ 1921 Great Britain.

ERNEST R. PURSER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,288,532 November 29, 1966 Harold E. Carver It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 14, line 15, strike out "a"; column 16, line 22, for "cutting and" read cutting head and Signed and sealed this 12th day of September 1967.

( AL) Attest:

ERNEST W. SWUJER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. A METHOD OF CONTINUOUS MINING IN A SUBTERRANEAN FORMATION COMPRISING: FORMING A SUBSTANTIALLY CONCAVE CONICAL FACE HAVING ITS VERTEX ADJACENT THE POINT OF DEEPEST PENETRATION INTO SAID FORMATION, SAID FACE COMPRISING A SERIES OF ANNULAR STEPS ABOUT ITS PERIPHERY WHICH INCREASE IN DIAMETER FROM SAID VERTEX REARWARD, EACH OF SAID STEPS BEING FORMED BY A RADIAL FACE NORMAL TO THE DIRECTION OF PENETRATION AND AN AXIAL FACE PARALLEL TO THE DIRECTION OF PENETRATION; CUTTING PERIPHERAL GROOVES INTO SAID FORMATION ADJACENT THE INTERIOR ANGLES FORMED AT THE JUNCTURE OF SAID 